Ceramic mix and method of preparing the same



Patented Jan. 11, 1944 CERAMIC MIX AND METHOD OF PREPARING THE SAME Cameron G. Harman, Urbana, Ill.

No Drawing. Application August 2, 1940, Serial No. 350,165

8 Claims.

This invention relates to an improved ceramic mix and method of preparing the same, and more particularly to a ceramic mix including a small proportion of a gelatinized cereal flour.

The preparation of ceramic materials by the plastic or dry press processes involves the mix-' ing of ceramic materials of the proper type followed by working, shaping, pressing, molding, turning, extruding, or other forming operation, after which the product is dried and fired. The present application does not relate to ceramic processes or articles made by processes in which the products are formed directly from melts, such as glass and glassware.

In carrying on the working and shaping processes there are several stages of the processes at which different difliculties may arise, depending upon the method being followed and the materials being employed. One of these ditflculties is lack of, or poor, flowability under pressure of certain materials. This may occur for example in extrusion, and equally as important but more limited in degree, in dry pressing in which it is desirable that the product assume the most compact form under a reasonably low pressure. The ability of the ceramic mix to flow may be increased by the use of a lubricant, and in this connection it has been discovered that gelatinized cereal flour, and particularly gelatinized corn flour, when used in the proper proportions, acts as a superior'lubricant to promote maximum .compacting under minimum pressure.

A second diiliculty frequently encountered is the lack of sufflcient rigidity and strength in ceramic articles prior to the time that they have been dried or fired. For example, many ceramic materials lack sufiicient strength before drying and the gelatinized corn flour provides an increase in strength in what is known as the green bonding strength of such materials.

Likewise, many ceramic materials are weak or easily broken or chipped after drying and before firing. The addition of a small percentage of gelatinized corn flour has a remarkable effect in increasing the dry strength of ceramic materials.

Some ceramic materials are shaped by extruding them through a die or by forcing them into a mold, and in some cases the ceramic mix lacks suflicient plasticity or moldability to permit this operation to be properly carried out. The additionof a small quantity of gelatinized corn flour acts as a superior plasticizing agent in this respect. There is unfortunately no adequate way of measuring plasticity so that a plasticity index cannot be categorically established. Experience in actual operation, however, has demonstrated clearly the value of the gelatinized material for this purpose.

It frequently happens that ceramic materials become too moist, either before or during mixing. Surprisingly enough, the addition of a small amount of gelatinized corn flour will overcome excess moisture and produce a suitabl workable material. This result is of particular value because, as it will be noted, the gelatinized corn flour material in this way makes a product which is too plastic to be properly workable, whereas, if the product is not plastic enough, it also improves its workability. The difliculties which have been set forth do not of course arise with all ceramic mixes and some of them are typical of one type of processing, whereas others are typical of a different type of processing. The present invention is particularly valuable because the addition of a small quantity of gelatinized corn flour to bring about a desired improvement in the body does not accentuate any of the difiiculties so that it may be added in the first instance without fear that it will adversely affect the processing which is to be carried out afterwards.

- As an example of the value of gelatinized cereal flour when employed as a lubricant to aid in the compacting of particles during dry pressing or dust pressing of ceramic articles, particles of calcined flint clay of definite particle size grading were-mixed in accordance with standard procedure and with them were included various proportions of gelatinized corn flour. In other samples, other materials were incorporated for the purpose of comparison of the lubricating eflects. In each case the materials were thoroughly mixed, the mixture was transferred quantitatively to a dry-press mold and the required pressure applied for three minutes. The mold was then 2,ssa,717

Table II shows the effect of the addition of gelatinized corn flour on the green bonding strength or particular ceramic mixes. The particular ceramic material is indicated in the first column. The corn product added is shown in column 2, per cent added is shown in column 3, and the method of gelatinization in column 4:

Test: II

Enect of corn products on the green bonding strength of ceramic mixes Compressive Ceramic material on1 product 53 figw stren be- Remarks Per cent mm. in.

2. 0 H t water 1110811 '.'.IIIIIIIIIII zo Afml 501116551111 Elastic.

38.5 a is sis-r. a: D. N s 0011 011....

on plum Gelstinised com flour.-. 2. 0 Hot rolls 30. 1

tarch 2.0 Alkalisolution- 46.4 Do

removed from the press and the volumeoi the pressed sample carefully measured.

The figures in Table I as follows, show the volume in cubic inches occupied in each case by 22.50 grams oi the ceramic material, the weight of any lubricant added being not included in this amount. The volumes are shown for each of three pressures, namely, 1,000 lbs., 2,000 lbs., and 3,000 lbs. per square inch. Even though the volume of lubricant added swells the true volume of the mix in the first instance, a small addition or gelatinized corn flour reduces the total bulk volume or the pressed mix. Too large an addition of gelatinized corn flour will obviously defeat the purpose for which it was intended. The optimum proportion of gelatinized cereal depends, of

course, on the properties of the ceramic materials in the mix, but will seldom exceed about Test: I

Influence of lubricants on the density of packing of ceramic mixes by dry pressing Volume in en. in. 0!

sample when subiectedtotheiollcwing Corn Amount Method oigelaproduct admixed tinization l,000 2, 3.000 lbs./in. lbsJin I lbsJin.

Percent 0.002 0.674 0.567 Gelstinised 0.5 Hotrolls 0.606 0.671 0.563

rn Do 1.0 --.do 0.507 0.577 0.564 Do 2.0 do 0.004 0.576 0.507 Corn flour 0.5 NaOH solution- 0.684 0.500 0.660 D0 0.5 Hotwnter 0.505 0.508 0.503 Do 0.5 Notseletinized. 0.590 0.500 0.659 "1? -2 is is as C mstnrc 0. o

0 Do 1.0 .do 0.590 0.570 0.002

Each sample contained 22.50 grams of calcined iilnt fire clay grains, the cereal product addition and 1.5 cc. otwater.

In Table III is shown the eflect of gelatlnized corn flour and other products on the dry strength of dry pressed ceramic materials. The ceramic material used in these tests was the same material which was the basis 01 Table I.

TABLIIII Eflect of various corn products on the dry strength of dry pressed ceramic mines Amount Method of gelacomm" Corn product strength in 45 admixed tinisstion dry m Per cent Lbs. in. Corn starch 0. 6 Not 'elatinlred In Do 2.0 n Corn flour 0. 5 so D0 2. 0 lo 40 Gelatinised corn floun. a a Hot rolls 400 Do l. 0 1 san Do 1. 6 I no Do- 2. 0 f n l, m Corn l. 0 Hot water 500 Corn iiour 1.0 ..-.-do Q0 1. 0 Alkali solution.. 040 None I] 55 It will be seen from the table that non-gelatioo nlzed starch and flour have substantially no eflect upon the compressive strength of the material. whereas the 'gelatinized material increases the strength at least thlrteenfold and in some cases as much as thirty-sevenfold.

Table IV illustrates the eitect of gelatinined corn flour and other products on the dry strength of clay of various types. The type of clay is illustrated in the first column and the type or material added is shown in the second column. As will be noted, the addition of corn. flour which had not been gelatinized, slightly reduced the modulus of rupture of the various materials, whereas the gelatinized material in all cases increased the modulus of rupture.

aaaam':

the dry strength of claws m of clay Corn product 3232:; a fight-Inlan $211 20! Per cent .LbL/lq. in.

5 .000 l. 1 m L 1,450 2.0 ,405 Plastic iirooiay L 0 3g 1.0 1,37 1,485 1,180 280 0. 5 440 1.0 mo Sandy shale 1. 5 790 1.0 345 1. 0 390 1.0 735 0. 5 5 0 w clay.-. 1:: 31 03 29g 0. 5 3 1.0 5 .f'f. 32 1. 0 2 5 1. 0 on n 271 f 'fi ffffiiffj 5:8 .1 3;: Corn flour l. 6 Alkali solution 933 Table V illustrates the effect of various corn products on the dry strength of non-plastic ceramic materials:

TABL: V

other example, dlaspore, when ground to mesh and finer, will not extrude at any water content.

With the addition of 2% of gelatinized corn flour,

Eflect of various corn products on the dry strength. of non-plastic ceramic mixes Ceramic material Corn product Method of gelatinization Modulus of rd turn, ad ad dry Flint clay grog Diaspore 0% x s,w% clay Sicmesh grains 0"" Corn starch.

Corn flour Gelatinized corn flour Com starch None...

Siliu brick mix 1 The plasticizing ability of the gelatinized corn iiour cannot be adequately defined, as already explained. It is possible, however, to show the amount of this material required to render a nonplastic material sufilciently plastic to be extruded from a die. For example, a fire clay grog comprising calcined and ground flint clay required 5% of g'elatinized cornflour to render it sufflciently plastic for extrusion, whereas, the same material required 10% of bentonite or 40% of pot clay. In each case the per cent is based upon this product in the same state of division wil. extrude in a still! column at the appropriate water content. The same material will extrude with v 1.5% of the geiatinized corn flour but not ve y well. The addition of 3% bentonite to diaspore of the same quality accomplishes the same results as the addition of 1.5% of gelatinized corn flour.

In all of the foregoing examples, the gelatinized cereal flour may be added to the ceramic materials before or during mixing. It added after mixing, an additional mixing operation is of the total mix, including the plasticizer. As ancourse desirable so that it is considered that the addition of the material after mixing is the equivalent of adding it'during or before mixing. Furthermore, the gelatinized material can be added either in the dry state or colloidally dissolved in water.

It has not been attempted in this application to exhaustively describe the various formative steps which are used in the various ceramic processes. Each ceramic process now known for the production of ceramic products, excepting glasses and enamels, of the type here discussed, utilizes one or more forming, shaping or working steps which are, in the proper case, assisted by the vance of its introduction into the ceramic material or mix. He may then add the gelatinized material in the liquid form, that is, the hydrolized cereal product will be in solution or suspended as a colloid in water.

It is more convenient, however, to use the form of material that has been gelatinized by passing the flour rapidly through hot rolls. This material is then pulverized and needs no further treatment to render it useful. It becomes active as soon as it is brought into contact with water, so has greater flexibility in its application than the floour which must be hydrolized by heating in water or by digesting in certain chemical solu-' tions.

The product may be carried into the completely gelatinized or hydrolized state, and is most suitable in some mixes when so prepared. However, in other mixes, for example those in which it is desired to improve the green strength. partial hydrolysis has been found to be better than complete hydrolysis.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom.

What I claim as new, and desire to secure by Letters Patent is:

1. A. ceramic mix including as an essential ingredient from approximately 0.5 to 2% of a gelatinized corn flour.

2. A ceramic mix including a large proportion of finely divided clayey material and approximately 0.5 to 2% of gelatinized com flour.

3. The method of improving ceramic mixes which comprises adding to a ceramic mix an amount not exceeding approximately 2% of a gelatinized corn flour, and uniformly distributing the flour through the ceramic mix.

4. The method of lubricating a dry ceramic mix which comprises distributing uniformly throughout finely divided ceramic material approximately 0.5% to 2% of a gelatinized corn flour, whereby the flow of the dry particles under pressure is substantially improved.

5. The method as set forth in claim 4, in which the cereal flour is gelatinized whole corn flour and it is added in an amout not exceeding approximately 0.5%.

6. The method oi improving the bonding strength of ceramic mixes which comprises blending with a ceramic mix a gelatlnized whole com 30 izlg ur in an amount not exceeding approximately 7. The method as set forth in claim 6, in which the cereal flour is gelatinized whole corn flour and it is added in an amount not exceeding ap- 36 proximately 2%.

, 8. A pressed ceramic mix including approximately 98% to 99.5% of ceramic material consisting essentially of a finely divided clayey ma terial and 0.5% to 2% of gelatinized corn flour,

40 the gelatinized corn flour being thoroughly distributed throughout the clayey material, the mixture having less volume than the volume of the ceramic mix under the same conditions without the addition of the gelatinized corn flour.

CAMERON G. HARMAN. 

